1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and an image processing program for processing an intraluminal image capturing an image of the inside of a lumen.
2. Description of the Related Art
Conventionally, endoscopes are popularly used as a medical observation apparatus introduced into the body of an examined subject such as a patient, to observe the inside of a lumen in the body. Also, in recent years, swallowed endoscopes (capsule endoscopes) have been developed that include, within a capsule-shaped casing, an image capturing device and a communication device that wirelessly transmits image data captured by the image capturing device to the outside of the body of the subject. It requires much experience to observe an image of the inside of the lumen in the subject's body (an intraluminal image) captured by such a medical observation apparatus and to make a diagnosis. Thus, medical diagnosis aiding functions that support medical doctors making a diagnosis are in demand. As an image recognition technique to realize such a function, a technique has been proposed by which an abnormal part such as a lesion is automatically detected from an intraluminal image and presented to a medical doctor or the like.
For example, Japanese Laid-open Patent Publication No. 2002-99896 discloses a technique by which candidates for microcalcification shadows, which serve as one of characteristics of a cancerized portion of breast cancer, are detected in a stable manner without being affected by macrostructures and linear-structures, while using shape-dependent filters. In this publication, based on a presumed shape of a microcalcification shadow, a second shape-dependent filter is prepared in advance by optimizing the filtering characteristic thereof according to various conditions such as an image-capturing condition, a reading condition, an image contrast, and a size of a microcalcification shadow, as well as conditions obtained by combining any of these conditions. First, a microstructure image showing a microstructure part is generated by eliminating straight-line structures from an image while using a first shape-dependent filter, which is a morphology filter (see, for example, KOBATAKE et al., “Extraction of Microcalcifications on Mammogram Using Morphological Filter with Multiple Structuring Elements”, The Transactions of the Institute of Electronics, Information and Communication Engineers, D-II, Vol. J75-D-II, No. 7, pages 1170-1176, July 1992; and KOBATAKE et al., “Basic Theory of Mathematical Morphology and its Application to Mammogram Processing”, MEDICAL IMAGING TECHNOLOGY, Vol. 12, No. 1, January 1994). After that, by applying an emphasizing process to the microstructure image while using the prepared second shape-dependent filter, an emphasized image is generated in which only candidates for microcalcification shadows are emphasized relative to the surrounding thereof (i.e., the parts that are other than the candidates for microcalcification shadows and that include macrostructure parts, and linear structure parts, and the like that were not eliminated by the first shape-dependent filter).